1. Field of the Invention
The present invention relates to an air-conditioner for an automobile and more particularly to an improvement in an air-conditioner for an automobile to control the cooling capacity without switching the compressor clutch on or off.
2. Description of the Prior Art
Conventionally the refrigerating circuit in an air-conditioner for an automobile is constituted as shown in FIG. 1 of the attached drawings. That is, in FIG. 1 the reference numeral 1 is a compressor, 2 is a condenser, 3 is a receiver-drier, 4 is an expansion valve, 5 is an evaporator, and 14 is a compressor clutch. In the refrigerating circuit comprising these elements connected in series, the refrigerant which has been compressed to a high temperature and high pressure by compressor 1 is transformed to a state in which it is at a normal temperature under the identical high pressure by the condenser 2, and after its pulsation has been eliminated in receiver-drier 3 the refrigerant is expanded by expansion valve 4, where the temperature and pressure are lowered, absorbing the heat in evaporator 5.
However, in this construction, in the case where at the time of high humidity in the passenger compartment only dehumidification of the compartment is to take place without lowering the temperature within the compartment, it has been found difficult to regulate the temperature, and also this circuit cannot be used for dehumidification unless a heating means is incorporated therewith. Further, since clutch 14 is used to transmit the rotation of the engine of the automobile to compressor 1, it brings about considerable problems in transmission loss, clutch life and also, due to its forming a considerable part of the overall weight of the compressor, in any weight reduction scheme.
A temperature-sensitive control system has been disclosed UK Patent Application GB No. 2 068 522A which comprises an automatic expansion valve and a control device, the automatic expansion valve being connected between the condenser and the evaporator to maintain a relatively constant pressure in the evaporator, and the control device includes a crankcase bypass valve which is responsive to the temperature of the refrigerant at the outlet of the evaporator for controlling the capacity of the compressor. However, this prior art does not teach the use of two compressing chambers adapted to be directly driven by an automobile engine, each having a different displacement for the control of the refrigerating capacity, i.e. the compressing chamber having a smaller displacement is always operated for dehumidification, while that having a larger displacement is only operated when the cooling is automatically or manually demanded.